1153
Inflamm Bowel Dis • Volume 27, Number 7, July 2021
Received for publications September 10, 2020; Editorial Decision November 10,
2020.
From the *Department of Biomedicine, Unity of Pharmacology and
Therapeutics, Faculty of Medicine of the University of Porto, Porto, Portugal;
†Department of Internal Medicine, Tâmega e Sousa Hospital Center, Padre
Américo Hospital, Penafiel, Portugal; ‡Department of Gastroenterology, Vila Nova
de Gaia/Espinho Hospital Center, Vila Nova de Gaia, Portugal; §Unit of Clinical
Pharmacology, São João Hospital Center, Porto, Portugal
Author Contribution: FJM, PPL, and MME contributed to the study concept and
design, acquisition of data, and analysis and interpretation of data. FM contributed to the
study concept and design, acquisition of data, analysis and interpretation of data, study
supervision, and critical revision of the manuscript for important intellectual content. All
authors read and approved the final version of the manuscript, including the author list.
Supported by: This work was supported by Grupo de Estudo da Doença
Inflamatória Intestinal (GEDII). FJM is supported by funding from Fondazione
Cariplo via the “Recruiting and Training Physicians-Scientists to Empower
Translational Research: A Multilevel Transdisciplinary Approach Focused on
Methodology, Ethics and Integrity in Biomedical Research” project (project grant:
02.00280, clinician scientist project).
Conficts of Interest: FM served as speaker and received honoraria from Merck
Sharp & Dohme, Abbvie, Vifor, Falk, Laboratórios Vitoria, Ferring, Hospira and
Biogen. All other authors have nothing to declare.
Address correspondence to: Fernando Magro, MD, PhD, Department of
Biomedicine, Unity of Pharmacology and Therapeutics, Faculty of Medicine of
the University of Porto, Rua Plácido da Costa, 4200-450 Porto, Portugal, E-mail:
fm@med.up.pt.
© The Author(s) 2020. Published by Oxford University Press on behalf of
Crohn’s & Colitis Foundation. All rights reserved. For permissions, please e-mail:
journals.permissions@oup.com
Basic science Review aRticle
The Role of Dipeptidyl Peptidase 4 as a Therapeutic Target
and Serum Biomarker in Inflammatory Bowel Disease:
A Systematic Review
Francisco Jorge Melo, MD,* Pedro Pinto-Lopes, MD,*,† Maria Manuela Estevinho, MD,*,‡ and Fernando Magro,
MD, PhD*,§
Background: The roles dipeptidyl peptidase 4 (DPP4), aminopeptidase N (APN), and their substrates in autoimmune diseases are being in-
creasingly recognized. However, their significance in inflammatory bowel diseases (IBD) is not entirely understood. This systematic review aims
to discuss the pathophysiological processes related to these ectopeptidases while comparing findings from preclinical and clinical settings.
Methods: This review was conducted according to the PRISMA guidelines. We performed a literature search in PubMed, SCOPUS, and Web
of Science to identify all reports from inception until February 2020. The search included validated animal models of intestinal inflammation
and studies in IBD patients. Quality assessment was performed using SYRCLE’s risk of bias tool and CASP qualitative and cohort checklists.
Results: From the 45 included studies, 36 were performed in animal models and 12 in humans (3 reports included both). Overall, the methodo-
logical quality of preclinical studies was acceptable. In animal models, DPP4 and APN inhibition significantly improved intestinal inflammation.
Glucagon-like peptide (GLP)-1 and GLP-2 analogs and GLP-2-relase-inducing drugs also showed significant benefits in recovery from inflamma-
tory damage. A nonsignificant trend toward disease remission with the GLP-2 analog teduglutide was observed in the sole interventional human
study. All human studies reported an inverse correlation between soluble DPP4/CD26 levels and disease severity, in accordance with the proposal
of DPP4 as a biomarker for IBD.
Conclusions: The use of DPP4 inhibitors and analogs of its substrates has clear benefits in the treatment of experimentally induced intestinal
inflammation. Further research is warranted to validate their potential diagnostic and therapeutic applications in IBD patients.
Key Words: pathogenesis, inflammation, translational, biomarker, ectopeptidase
INTRODUCTION
Inflammatory bowel diseases (IBDs) are a group of
chronic relapsing autoimmune disorders, comprising Crohn’s
disease (CD),1 ulcerative colitis (UC),2 and an intermediate
spectrum of unclassifiable conditions designated as indeter-
minate colitis.3 Inflammatory bowel disease present many
extraintestinal manifestations and may pertain to a cluster
of autoimmune diseases affecting the same patient.4 Left un-
treated, these conditions are highly debilitating and potentially
life-threatening and represent a high economic burden.1, 2, 4
In recent decades, IBD has been the target of intensive
research, with considerable progress in the therapeutic man-
agement of the disease and related pathologies. However, most
available treatment strategies have a significant amount of
nonresponders and a wide range of adverse effects.1, 2 Thus,
the development of new and optimized therapeutic weapons is
now supported by research on the underlying pathophysiolog-
ical mechanisms of IBD.
Dipeptidyl peptidase 4 (DPP4), homologous to cell-
surface marker CD26 (cluster of differentiation 26), is a
near-ubiquitous membrane protease that cleaves N-terminal
dipeptides from many endogenous and exogenous peptides.5
doi: 10.1093/ibd/izaa324
Published online 9 December 2020
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Inflamm Bowel Dis • Volume 27, Number 7, July 2021
This enzyme is well-known for its physiological action in the
incretin axis as the main cause for the rapid inactivation of the
incretins glucagon-like peptide (GLP)-1 and gastric inhibitory
polypeptide (GIP).5 The GLP-1 analogs and DPP4 inhibitors
(DPP4i), which act by increasing the half-life of endogenous
GLP-1, are potent insulinotropic drugs used in the therapy of
diabetes mellitus.6, 7
In the last 2 decades, interest in DPP4, aside from its
utility in glycemic control, has grown. In fact, plasma levels of
this protein have been inversely correlated with disease severity
in IBD and other autoimmune diseases (ADs), making it a po-
tentially new biomarker and a valid therapeutic target for these
conditions.8
The 766-amino acid (aa) CD26/DPP4 is a membrane pro-
tein, with many distinct physiological roles (Fig. 1). It contains
an independent C-terminal catalytic region, a cysteine-rich re-
gion, a glycosylation-rich region, a flexible stalk, a transmem-
brane domain, and a short cytosolic tail. It presents specific
binding sites to fibronectin (and other extracellular matrix
components) and extracellular adenosine deaminase (ADA).9
After dimerization, CD26/DPP4 is able to activate intracellular
signaling pathways as a type 2 membrane receptor.5 The mech-
anism underlying its cleavage and shedding to plasma in its sol-
uble form, sCD26/DPP4 (aa 39–766), is still unclear.10 Either
through direct cell-signaling or by cleaving immune mediators,
it interferes in several immunoregulatory processes.9 By binding
to caveolin-1 on the surface of antigen-presenting dendritic cells
(DCs), DPP4/CD26 stimulates the expression of costimulatory
CD86, through NF-κB signaling, thereby promoting T-cell ac-
tivation.11 Cosignaling with CD45, it enhances T-cell expression
FIGURE 1. Proposed mechanistic view of CD26/DPP4-centered interactions in intestinal inflammation—Th1-polarizing perspective. Membrane
CD26/DPP4, coupled to CD45 in naïve T helper cells, directly stimulates NF-κB-dependent T-cell activation and differentiation into a Th1 phenotype.
Additionally, it proteolytically cleaves N-terminal dipeptides from a variety of substrates, including GLP-1, GLP-2, VIP, and NPY. GLP-1 is a negative
regulator of NF-κB and costimulatory DC signals. GLP-2, acting via GLP-2R, is an intestinotrophic peptide that stimulates the production and release
of intestinal growth factors (EGF, KGFR, IGF-1), which stimulate iSC proliferation and differentiation, effectively counteracting mucosal inflamma-
tory lesions. GLP-23–33 acts as partial agonist/antagonist at GLP-2R. VIP is a negative regulator of neutrophil and lymphocyte chemotaxis and inhibits
macrophage activation. NPY is an ENS-derived pro-inflammatory peptide. CD26/DPP4 is shed to plasma through a mechanism not yet completely
understood. Abbreviations: BNP, brain natriuretic peptide; CCL/CXCL, Chemokines; CCR/CXCR, Chemokine receptors; CD, cluster of differentiation;
DC, dendritic cell; ENS, enteric nervous system; EGF, epidermal growth factor; GHRH, growth hormone-releasing hormone; GIP, gastric inhibitory pol-
ypeptide; GLP-1/-2/-1R/-2R, glucagon-like peptide 1/2/1-receptor/2-receptor; GPR40, G-protein coupled receptor 40 (FFA1, free fatty acid receptor
1); GPR120, G-protein coupled receptor 120 (FFA4, free fatty acid receptor 1); IGF-1/-1R, insulin-like growth factor 1/1-receptor; IL, interleukin; IFN-γ,
interferon-gamma; iSC, intestinal stem cell; iSEMF, intestinal sub-epithelial myofibroblasts; KGF/KGFR, keratinocyte growth factor/receptor; MMP,
matrix metallopeptidase; nNOS, neuronal nitric oxide synthase; NO, nitric oxide; NPY, neuropeptide Y; PACAP, pituitary adenylate cyclase-activating
polypeptide; PYY, peptide YY; sCD26/DPP4, soluble CD26/DPP4; SDF-1/CXCL12, stromal cell-derived factor 1; SP, substance P; TGR5, G-protein
coupled bile acid receptor 1 (GPBAR1); Th, T helper cell; TNF-α, tumor necrosis factor alpha; VIP, vasoactive intestinal peptide; Y1, NPY receptor type
1. Substrates in orange have altered receptor subtype specificity after cleavage by DPP4. Substrates in black mainly lose their bioactivity.
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Dipeptidyl Peptidase 4 as a Therapeutic Target and Serum Biomarker in IBD
Inflamm Bowel Dis • Volume 27, Number 7, July 2021
of interleukin (IL)-2 and ultimately contributes to differentia-
tion into a T helper (Th) 1 phenotype.12, 13 Adenosine deaminase
binding to CD26 colocates ADA to the cell surface, allowing
local degradation of adenosine (a known inhibitor of T-cell
activation) to inosine, hence controlling its extracellular levels
at the immunological synapse. Furthermore, ADA binding to
CD26 was found to produce a direct costimulatory response in
T-cell activation.14, 15
Many bioactive or inactive precursor peptides are sub-
strates of DPP4, including peptide hormones (GLP-1, GLP-
2), neuropeptides (neuropeptide Y, substance P), and many
chemokines and growth factors. Additionally, this enzyme acts
as long as the penultimate amino acid is either proline or ala-
nine. It is also capable of cleaving N-terminal X-glycine/serine/
valine/leucine, albeit at a slower rate. Cleavage is hindered by
the presence of proline in NH2-Xaa-Xaa-Pro position.5 In in-
flammatory settings, the most relevant substrates of DPP4 are
GLP-1, GLP-2, and vasoactive intestinal peptide (VIP).
In addition to its insulinotropic action, GLP-1, acting
through GLP-1R, stimulates protein kinase A (PKA) and
leads to the inhibition of the T-cell costimulatory CD28/
CD86 signal.16 It is rapidly inactivated by DPP4 into GLP-
19–36/7, with a short half-life of around 1 to 4 minutes.17 The
GLP-2 is a sister molecule of GLP-1 that is co-expressed and
coreleased from enteroendocrine L cells, after processing of
their common precursor, proglucagon. Through its receptor,
GLP-2R, localized in enteric nervous plexuses (myenteric, sub-
mucosal)18 and subepithelial myofibroblasts,19 stimulates the
release of key intestinal growth factors such as KGF, IGF-1,
and EGF; this mechanism reverts inflammatory changes in
the intestinal epithelium.20, 21 As with GLP-1, GLP-2 is rap-
idly inactivated by local DPP4 to GLP-23–33, with a half-life of
7 minutes; however its metabolite has a half-life of around 27
minutes.22 Additionally, GLP-23–33 acts as a competitive inhib-
itor of GLP-2 at GLP-2R.22 Teduglutide, a DPP4-resistant long
half-life GLP-2 analog, is approved for use in short bowel syn-
drome and is under investigation for its applicability in IBD.23
In addition, GLP-2 stimulates the release of VIP from enteric
neurons.24 Vasoactive intestinal peptide is a 28-amino acid pep-
tide with a short half-life of around 1 minute and a wide range
of effects, including neurotransmitter, immunomodulatory,
and secretagogue activities.25, 26 It inhibits TNF-α production
by macrophages27 and promotes TH cell differentiation toward
a Th2 phenotype.28
Aminopeptidase N (APN) is an ectopeptidase homolo-
gous to CD13.29 It is being studied in the setting of hemato-
logical disorders and gained interest as a potential co-effector
of DPP4/CD26 in immune regulation.30 Aminopeptidase
N is involved in antigen processing and interaction with ex-
tracellular matrix proteins.30 Its substrates include several
immunoregulatory molecules.30 It cleaves off N-terminal neu-
tral amino acids of oligopeptides but stops if proline is in
the penultimate position.31 These catalytic specificities, the
subcellular localization similar to CD26, and increased expres-
sion in activated T cells point to a potential role of APN/CD13
as a DPP4/CD26-substrate generator and vice versa, acting in
tandem as regulators of immune responses. This is further sup-
ported by an improved anti-inflammatory response of the dual
APN/DPP4 inhibition compared with antagonism of only one
of either of these proteins.32 For this reason, we decided to ex-
tend the scope of this review to also include reports on the role
of APN/CD13 in intestinal inflammation.
Although some reviews on the importance of DPP4 and
APN on AIDs and inflammation have been published, the
knowledge on their specific role in IBD pathogenesis is lim-
ited. This systematic review aims to fill this gap and provide a
link between preclinical and clinical data on the role of these
ectopeptidases in IBD (as well as other molecules of their re-
lated axes), through the use of validated animal models of in-
testinal inflammation33 and studies on IBD patients.
METHODS
This review was conducted following the recommenda-
tions of the Preferred Reporting Items for Systematic Reviews
and Meta-Analyses Statement (PRISMA 2009).34 Study
screening was conducted in 3 electronic databases: PubMed,
Web of Science, and SCOPUS, covering all reports published
through February 4, 2020. The query used for PubMed was as
follows: “DPPR OR DPPIV OR Dipeptidyl peptidase 4 OR
Dipeptidyl peptidase IV OR CD26 OR ADCP2 OR Adenosine
deaminase complexing protein 2 OR Aminopeptidase N OR
Alanyl aminopeptidase OR Alanine aminopeptidase OR CD13
OR AAP OR APN AND inflammatory bowel disease OR
crohn’s disease OR ulcerative colitis.” Similar queries were used
for the other 2 databases, after syntax adaptation. To ensure
the inclusion of all pertinent studies, the reference lists of the
included reports were reviewed by 2 independent researchers.
All preclinical reports emphasizing the pathophysiolog-
ical role of DPP4/CD23 and APN/CD13 in intestinal inflam-
mation models, in addition to clinical reports demonstrating a
link between DPP4/APN and IBD, were assessed for inclusion.
Reports concerning other molecules pertaining to the physio-
logical axes of these factors were also considered, as long as
there was at least an indirect link to DPP4 or APN.
The inclusion criteria were (1) articles studying the asso-
ciation between DPP4/CD26 and IBD in animal models of in-
testinal inflammation and human patients; (2) articles studying
the association between APN/CD13 and IBD in animal models
of intestinal inflammation; and (3) articles studying the associ-
ation between related molecules of the DPP4 axis with known
therapeutic potential, specifically GLP-1 and GLP-2 (and mol-
ecules that influenced GLP-1 or GLP-2 levels, such as TGR5,
G-protein coupled receptor [GPR]-40, and GPR120), and IBD
in animal models of intestinal inflammation and human pa-
tients. No restrictions on publication language were applied.
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The exclusion criteria were (1) review papers, metanalyses,
letters, commentaries, guidelines, editorials, meeting abstracts,
and case reports; (2) studies with no relation to IBD or related
animal models of colitis (intestinal cancer studies, radiation-
induced injury, etc.); (3) studies with no pathophysiological
association with DPP4 or APN; (4) studies including other
substrates of DPP4 and APN (setting a limit to study screening
and to avoid an overreaching and unfocused review of all pos-
sible substrates and their influence in DPP4-dependent inflam-
matory pathways); and (5) studies without available abstract.
The risk of bias in individual studies was assessed using
quality evaluation tools/scales adapted to study type. For pre-
clinical animal studies, SYRCLE’s risk of bias (RoB) tool was
used.35 For studies in humans, CASP checklists were used for
qualitative36 and cohort37 reports. These tools were applied
by 2 independent reviewers, and discrepancies were solved by
consensus.
RESULTS
Study Selection and Characteristics
Study selection, following the PRISMA 2009 Flow
Diagram,34 is outlined in Figure 2. Of the 45 studies selected for
review, 36 used animal models of intestinal inflammation,38–73
and 12 concerned human IBD patients50, 66, 67, 74–82 (3 reports
included both50, 66, 67). The characteristics and main results of
animal studies are described in Supplementary Table 1 and
those of human studies in Table 1. For animal studies, disease
and animal models, with respective variations, are compiled in
Supplementary Table 2.
Most animal studies consisted of interventional proto-
cols of varying durations that tested the effects of DPP4i,
APNi, GLP-1, or GLP-2 analogs (mostly long-acting, DPP4-
resistant, or by continuous infusion) and related drugs on the
recovery from experimentally induced intestinal lesions.
The most used model of colitis was the dex-
tran sulfate sodium (DSS) model (n = 25), followed by
2,4,6-trinitrobenzenesulfonic acid (TNBS, n = 7), indomethacin
(n = 5), HLA-B27 (n = 2), CD4+ transfer (n = 1), and irinotecan
(n = 1) models. The most commonly used strains of mice were
Balb/c and C57BL/6 mice. Seven reports utilized knock-out
mice for CD26/DPP4, and 1 study used Glp2r−/− mice.
Despite wide variations in protocol, we decided to inter-
pret each model’s group as a whole, inasmuch as all experiments
were able to elicit an inflammatory response to some extent and
were therefore deemed internally valid.
With a single exception of an interventional study,74 all
studies in human IBD patients were observational, focusing
on serum activity, levels of DPP4, APN, GLP-2, GLP-2R, and
others, in addition to associated clinical and endoscopic find-
ings. None of the included studies in IBD patients used DPP4
inhibitors.
FIGURE 2. Study screening and selection process.
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Dipeptidyl Peptidase 4 as a Therapeutic Target and Serum Biomarker in IBD
Inflamm Bowel Dis • Volume 27, Number 7, July 2021
TABLE 1. Characteristics and Main Results of Human Studies
Authors (Year)
Study
Origin
Study Type IBD
IBD
Assessment
Disease Character-
istics
Intervention
Outcomes Assessed
Results
Buchman AL et al
(2010)
USA and
Canada
(multicenter)
Prospective
(pilot)
CD, moderate-
to-severe (n
= 100)
(Extension: n
= 48)
CDAI
CDAI 220–450
Mean disease duration
11.1–13.7 ± 9.5–10.9
24% concomitant
therapy with
immunomodulators
Teduglutide
0.05/0.10/0.20
mg/kg/d, sc,
1id, 8w
(Extension:
teduglutide
0.10 mg/kg/d,
sc, 1id, for
12 additional
weeks)
Primary: response (100pts
CDAI) or remission (CDAI
≤ 150) at week 8;
Secondary: response and
remission at weeks 2 and
4, mean changes in disease
severity (CDAI), mean de-
crease in # of liquid bowel
movements, mean decrease
in CRP.
No statistically significant dif-
ferences from placebo.
In the 0.2 mg/kg/d group, 40%
achieved remission at 8 weeks.
No difference was observed
in serum CRP at any
timepoint.
Plasma citrulline substantially
increased over time in all
teduglutide groups.
El-Jamal N et al
(2014)
Not
reported
Cross-sec-
tional
CD (n = 19)
UC (n = 15)
Not reported
Insufficient data
—
GLP-2R expression in human
intestine of IBD patients.
Significantly higher expression
of GLP-2R mRNA in the
colon of healthy and IBD
patients, vs in the ileum.
Significantly lower levels of
GLP-2R mRNA in healthy
colon and ileal samples
from CD patients, vs con-
trols; and further significant
reduction in inflammed
samples, vs healthy samples;
Significantly lower levels of
GLP-2R mRNA in healthy
ileal samples from UC
patients, vs controls; and
further significant reduction
in inflammed samples, vs
healthy samples;
Significantly lower levels
of GLP-2R mRNA in
inflammed colon samples
from UC patients, vs con-
trols, but no difference in
healthy colon samples of
UC patients, vs controls.
Hildebrandt M et
al (2001)
Germany,
single
center
Cross-sec-
tional
CD (n = 63)
UC (n = 47)
Controls (n =
28)
CDAI
Rachmilewitz
score (UC)
Mean disease duration
CD: 10.8 ± 8.1 s
years
UC: 11.9 ± 8.5 s years
—
sDPP4 activity and lympho-
cyte CD26/DPP4 expres-
sion in IBD patiens.
Similar percentages of CD2+/
CD26+ cells in peripheral
blood between patients and
healthy controls.
Higher number of CD25+/
CD26+ and CD2+/CD25+
cells in IBD patients.
DPP4 activity was inversely
correlated with disease
activity, orosomucoid con-
centrations and CRP.
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1158
Melo et al
Inflamm Bowel Dis • Volume 27, Number 7, July 2021
TABLE 1. Continued
Authors (Year)
Study
Origin
Study Type IBD
IBD
Assessment
Disease Character-
istics
Intervention
Outcomes Assessed
Results
Magro D et al
(2017)
Brazil, single
center
Cross-sec-
tional
CD (n = 20)
CDAI
(active: >150;
remission:
≤150)
Montreal
Classifica-
tion
Active CD: n = 10
Remiting CD: n = 10
—
Correlation between serum
levels of LPS and CD26,
and serum levels of CRP,
interleukins, TNF-a and
CDAI.
Significantly higher levels of
serum LPS amd CRP in ac-
tive and inactive CD group,
vs controls.
Significantly lower levels of
IL-1β, IL-6, IL-17 and
CD26 in CD groups, vs
controls.
Nonsignificant higher level of
TNF-α in active CD group,
vs control (p = 0.056).
Negative correlation be-
tween CRP and LPS in CD
groups.
Moran GW et al
(2012)
Not reported Cross-sec-
tional
CD (n = 26)
CDAI
CRP
CDAI = 174.5 ± 14.26
CRP = 20.4 ± 5.4
mg/L
—
DDP4 expression and correla-
tion to underlying intes-
tinal inflammation (CDAI,
CRP).
Significantly lower levels of
plasma and tissue (terminal
ileum) DPP4 in CD pa-
tients, vs controls.
Significant negative correla-
tion between plasma DPP4
and CRP.
Pinto-Lopes P et
al (2020)
Portugal,
multicenter
Prospective
cohorts
CD (n = 101)
UC (n = 94)
Controls (n =
52)
CD: HBI (clin-
ical remis-
sion: ≤4)
UC: pMS
(clinical
remissio: ≤1)
Montreal
Classifica-
tion
Active CD: HBI = 7.6
± 3.2
Remitting CD: HBI =
1.4 ± 1.3
Active UC: pMS = 4.7
± 2.3
Remitting UC: pMS =
0.1 ± 0.3
—
Role of sDPP4 as a biomarker
of IBD activity (potential
in predicting the need for
treatment escalation and
monitoring response to bio-
logical therapy); correlation
between sDPP4 levels with
endoscopic activity and
clinical activity scores.
Patients with active IBD had
significantly higher serum
CRP and FC levels and
lower sDPP4, vs those in
clinical remission.
sDPP4 levels were negatively
correlated with FC, serum
CRP and DAI.
FC was positively correlated
with serum CRP and DAI.
sDPP4 was inversely cor-
related with both disease
activity scores (HBI and
pMS) and endoscopic ac-
tivity groups (stronger in
CD, vs UC).
sDPP4 activity was signifi-
cantly higher in responders
(stronger in UC, vs CD).
Salaga M,
Mokrowiecka
A, Zielinska M
et al (2017)
Not
reported
Cross-sec-
tional
CD (n = 9)
UC (n = 12)
Controls (n = 8)
13 colon biopsy
samples
29 serum sam-
ples
Montreal
Classifica-
tion
CD:
5-ASA (n = 5)
Anti-TNF-a (n = 4)
UC:
5-ASA (n = 12)
—
Expression of GLP-2 and
GLP-2R in the serum and
colon of IBD patiens.
Significant decrease in the ex-
pression of serum GLP-2 in
CD patients.
Significant decrease in the ex-
pression of colon GLP-2R
in UC patients.
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Dipeptidyl Peptidase 4 as a Therapeutic Target and Serum Biomarker in IBD
Inflamm Bowel Dis • Volume 27, Number 7, July 2021
Authors (Year)
Study
Origin
Study Type IBD
IBD
Assessment
Disease Character-
istics
Intervention
Outcomes Assessed
Results
Salaga M,
Mokrowiecka
A, Jacenik D et
al (2017)
Not reported Cross-sec-
tional
CD (n = 17)
UC (n = 10)
Controls (n
= 8)
35 colon bi-
opsy samples
56 serum sam-
ples
Montreal
Classifica-
tion
CD:
5-ASA (n = 10)
Anti-TNF-a (n = 7)
UC:
5-ASA (n = 10)
—
Characterization of intestinal
tissue and serum expression
levels of APN and NEP in
IBD patients.
Significantly higher expression
of APN mRNA in colonic
tissue of CD patients
(nonsignificant increase in
UC patients).
Nonsignificant increase in the
expression of NEP protein in
colonic tissue of CD patients.
No changes in serum levels.
Schmidt PT et al
(2005)
Sweden,
single
center
Cross-sec-
tional
CD (n = 4)
UC (n = 15)
Controls (n =
10)
Not reported
Active disease:
CD (n = 4)
UC (n = 5)
Chronic/no inflamma-
tion:
UC (n = 10)
CD:
5-ASA (n = 1)
Glucocorticoids (n
= 1)
Metronidazole (n = 1)
UC:
5-ASA (n = 11)
Prednisolone (n = 1)
Azathioprine (n = 1)
Meal stimu-
lation (430
kcal)
Tissue levels and postprandial
secretion of GLP-2 and
PYY in IBD patients.
No significant differences in
tissue content or plasma
concentration after meal
stimulation of GLP-2 and
PYY between IBD patients
and controls.
Tsukahara T et al
(2015)
Japan, single
center
Cross-sec-
tional
CD (n = 16)
Controls (n =
15)
Not reported
Previous therapeutic
exposure:
Anti-TNF-a (n = 4)
Immunomodulator
(n = 2)
Corticosteroids (n
= 0)
—
Expression of GPR40 and
GPR120 in the ileal mucosa
of CD patients and its cor-
relation with inflammatory
parameters.
Intestinal epithelial cells
express GPR40, but rarely
express GPR120, in the
normal ileal mucosa. Boh
were overexpressed in in-
flamed ileal mucosa.
GPR40 and GPR120 are
co-expressed in L cells (signifi-
cant positive correlation).
HBI values significantly
correlated with GPR120 ex-
pression, but not GPR40.
Signficiantly higher levels of
TNF-α.
Both GPR120 and GPR40
expression levels signifi-
cantly correlated with levels
of TNF-α, but not those of
IL-6 or IL-1β.
No differences in protein
and mRNA expression of
proglucagon in CD patients
vs controls.
TABLE 1. Continued
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Authors (Year)
Study
Origin
Study Type IBD
IBD
Assessment
Disease Character-
istics
Intervention
Outcomes Assessed
Results
Varljen J et al
(2005)
Croatia,
single
center
Cross-sec-
tional
CD (n = 38)
UC (n = 24)
CDAI
UC: Truelove
and Witts’
(TW) classi-
fication
Insufficient data
—
Relation between sDPP4
activity with clinical and
inflammatory parameters in
patients with IBD; potential
of sDPP4 activity as a dis-
tinguishing marker between
CD and UC.
sDPP4 activity was signifi-
cantly decreased in both CD
and UC patients, vs con-
trols, although no signficant
differences were found be-
tween the 2 IBD groups.
DPP4 activity inversely correl-
ates with CDAI score in CD
patients, and TW in UC
patients.
Significant difference in sDPP4
activity between male and
female patients with UC.
No correlation between
sDPP4 activity and routine
laboratory parameters in ei-
ther disease, nor in relation
to the location and exten-
sion of pathological lesions.
Xiao Q et al
(2000)
Canada,
single
center
Cross-sec-
tional
GLP-2
CD (n = 39)
CD without
bowel resec-
tion (n = 30)
CD with bowel
resection (n
= 9)
UC (n = 21)
Healthy con-
trols (n = 14)
Immune con-
trols (n = 38)
DPP4
CD without
bowel resec-
tion (n = 1)
CD with bowel
resection (n
= 5)
UC (n = 1)
Healthy con-
trols (n = 6)
Not reported
Mean disease duration
GLP-2
CD without bowel
resection: 4.5 ± 5.1
years
CD with bowel resec-
tion: 12.9 ± 12.7
years
UC: 4.3 ± 5.9 years
DPP4
CD without bowel
resection: 8 years
CD with bowel re-
section: 14.3 ± 3.8
years
UC: 1 year
—
Abnormalities in the levels
and/or molecular forms of
circulating GLP-2 in IBD
patients.
No differences between
plasma levels of total
immunoreactive (IR)-
GLP-2 between normal
healthy and immunocom-
promised control subjects,
and between normal con-
trols and UC patients.
Total plasma IR-GLP-2 levels
were significantly decreased
in CD patients, vs controls.
No differences in total
IR-GLP-2 levels between
CD subgroups according to
disease site, but significant
decrease in total IR-GLP-2 in
CD patients who had a his-
tory of intestinal resection.
Significantly higher bioac-
tive GLP-21–33 levels in IBD
patients (higher ratio of
GLP-21–33 to GLP-23–33).
Significantly lower plasma
DPP4 activity in IBD pa-
tients, vs normal controls.
Abbreviations: CD#, cluster of differentiation #; CDAI, Crohn’s disease activity index; DAI, disease activity index; HB, Harvey-Bradshaw index; IFN-γ, interferon-gamma; LPS, lipopolysaccharide; pMS, partial
Mayo score; Th, T helper cell; TNF-α, tumor necrosis factor alpha; 5-ASA, 5-aminosalicylic acid/mesalazine
TABLE 1. Continued
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Dipeptidyl Peptidase 4 as a Therapeutic Target and Serum Biomarker in IBD
Inflamm Bowel Dis • Volume 27, Number 7, July 2021
Quality Assessment
The results of the methodological quality evaluation are
summarized in Supplementary Tables 3–5. Overall, preclinical
studies do not report sufficient details to allow for proper risk of
bias assessment, with most items being answered as “unclear,”
according to SYRCLE’s RoB tool35 (Supplementary Table 3).
Unlike randomized clinical trials (RCTs), experimental studies
in animals usually do not implement tools to assess internal va-
lidity and risk of bias in their study design. Consequently, the
generalizability of their findings is compromised due to poor re-
porting.35 In the revised studies, the most affected domains were
inadequate randomization during allocation of study groups
and outcome assessment and lack of blinding/concealment.
For the included reports on human patients, we used 2
separate CASP checklists, according to study design: qualita-
tive36 (Supplementary Table 4) and cohort37 (Supplementary
Table 5). Human qualitative studies showed a better perfor-
mance under appraisal when compared with animal studies due
to better reporting. Nevertheless, some doubts arise (eg, “Can’t
tell”) in the items related to adequate recruitment, representa-
tiveness, and significance of the study population. Furthermore,
the studies revealed a low ability to extrapolate findings to the
general population, most often due to low sample size and high
homogeneity (eg, only female subjects, only recruited from ter-
tiary centers, etc.). As expected, cohort studies had better clas-
sifications, yet the generalizability of the results was also an
important drawback.
DPP4/CD26 and APN/CD13
Animal studies
None of the studies in CD26−/− mice with experimentally
induced colitis showed significant differences in histological
and clinical scores compared with wild-type strains.44, 46–48, 53
Conversely, Iwaya et al56 demonstrated a significant yet tran-
sient improvement of intestinal inflammation in an early phase
of colitis development in DPP4-deficient (F344/Du) rats.
Reports using DPP4 inhibitors showed either partial or
significant improvement of clinical and histological scores and
reduction of MPO activity and pro-inflammatory cytokine
levels.42, 43, 51, 52, 55, 61, 65, 67, 71–73
Bank et al43 studied the effects of combined inhibition of
both DPP4 and APN on colitis attenuation. The dual DPP4/
APN inhibitor IP12.C6 promoted the expression of TGF-β and
FOXP3 compared with separate inhibition and controls. In a
similar manner, dual inhibition of APN and neprilysin (NEP,
CD10) by sialorphin or a sialorphin analogue also significantly
improved colitis, in part through µ- and κ-opioid receptor-
dependent mechanisms.57, 66
Human studies
Serum CD26/DPP4 expression and/or activity was found
to be significantly lower in IBD patients compared with healthy
controls.75–77, 80–82 Patients with active disease showed lower
levels than patients in remission, and sCD26/DPP4 levels were
negatively correlated with disease severity and classical inflam-
matory markers, such as C-reactive protein (CRP).75, 77, 80, 82 In
addition, Hildebrandt et al82 reported significant increases in
CD25+/CD26+ and CD2+/CD25+ peripheral blood lymphocytes
in IBD patients vs controls but no differences in the popula-
tion of CD2+/CD26+ cells. Moran et al76 showed that DPP4 ex-
pression was significantly reduced in tissue samples from the
terminal ileum of IBD patients. Still, the authors reported sig-
nificantly higher levels of DPP4 in a Caco-2 cell-based study
after exposure to rhTNF-α.76 As with similar reports, they
showed an inverse correlation between serum DPP4 (sDPP4)
levels and CRP; however, such correlation was not found for
CDAI.76
In a recent multicentric prospective cohort undertaken by
our study group,77 sDPP4 was found to have a strong inverse
correlation with clinical and endoscopic activity. It performed
equally well in postoperative CD patients. Optimal cutoff
points were defined based on receiver operating characteristics
(ROC) curve analysis of sDPP4 and 2 other biomarkers, CRP
and fecal calprotectin (FC). These were used to predict clinical
activity, endoscopic activity, and treatment escalation in both
CD and UC patients. Stratification according to these cutoffs
in a Kaplan-Meier curve showed that after 1 year, 62.2% of
CD patients and 36.3% of UC patients with DPP4 levels below
the cutoff (≤1452 ng/mL and ≤1472 ng/mL, respectively) had
escalated treatment, as opposed to 7.8% of CD and 4.1% of
UC patients with DPP4 levels above the cutoff. The use of 3 si-
multaneous biomarkers proved to have a higher discriminative
power. Eighty percent of the CD patients with 3 positive bio-
markers escalated treatment after 1 year vs 3.3% of the patients
with triple negative biomarkers. Regarding UC, 85.0% of the
patients with 3 positive biomarkers escalated treatment after
1 year vs none with 3 negative biomarkers. All 3 biomarkers
had a similar ability to distinguish between IBD responders and
nonresponders. In a subset of the IBD population with active
disease but without CRP elevation, sDPP4 was able to discrim-
inate endoscopic activity better than FC.
Aminopeptidase N mRNA expression was significantly
higher in colonic tissue of CD patients (nonsignificant increases
in UC patients and in the expression of NEP protein levels in
CD patients), but no changes were detected in serum levels.66
Glucagon-like Peptides
Animal studies
Thirteen reports studied the effects of GLP-2, either
by continuous infusion,38, 41 long-acting polymer-coupled
(XTEN,39 PEG62, 63) or microsphere-associated69 molecules, or
degradation-resistant analogs.45, 49, 54, 60, 70 These studies reported
significant improvements in histological and clinical scores, re-
duction in pro-inflammatory cytokine levels and MPO activity,
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and a significant intestinal growth (intestinotrophic) response.
This was assessed by increased crypt cell proliferation and in-
creased survival/reduced apoptotic rates and manifested by
decreased intestinal length reduction after experimental in-
duction of inflammation. A study conducted in Glp2r−/− mice
demonstrated a functional Paneth cell defect, with reduced
bactericidal activity and reduced expression of intestinotrophic
factors.59 Furthermore, similar outcomes were obtained by ac-
tivation of GPR40 (FFAR1, free fatty acid receptor 183) and
TGR5 (GPBAR1, G protein-coupled bile acid receptor 184) in
enteroendocrine L cells by specific agonists with increased ex-
pression and release of GLP-2.58, 64
A report on GLP-1 nanomedicine revealed a significant
decrease of pro-inflammatory cytokine IL-1β levels and tissue
damage, in addition to a partial attenuation of the diarrheal
phenotype.40
Human studies
In accordance with the results in animal models, a pilot
study74 of a marketed GLP-2 analog, teduglutide, demon-
strated a trend toward an increased response and remission rate
in IBD patients, although these differences were not statistically
significant. A significant increase in plasma citrulline levels, an
indirect marker of intestinal mucosal mass, was also reported.
Other human studies found lower expression of GLP-2R
and GLP-2 in an inflammatory setting in IBD patients com-
pared with noninflamed sites and healthy controls.50, 67, 78, 81
Schmidt et al78 found no differences in tissue or plasma levels of
GLP-2 or peptide YY (PYY) after meal-stimulation between
IBD patients and healthy controls.
A report on CD patients showed overexpression of both
GPR40 and GPR120 (FFAR4, free fatty acid receptor 4)85 in
inflamed ileal mucosa and a GPR120-dependent inhibition of
GPR40-induced GLP-2 expression by L cells, promoted by
upregulation of GPR120 by TNF-α.79
DISCUSSION
Dipeptidyl peptidase 4/CD26 and its substrates have been
recognized as important mediators of inflammation and immu-
nity. However, data on the efficacy of manipulating the incretin
axis as a treatment modality in IBD lack consistency.49, 70, 74
Despite the success of DPP4 inhibitors as antidiabetic
drugs, the use of DPP4 inhibitors raises special concerns re-
garding the potential short and long-term adverse effects of
inhibiting a molecule with such a broad spectrum of inter-
actions. This is conditioned by the specific cell population
expressing this protein; the local availability, half-life, and bi-
oactivity of its substrates; reaction rates; and substrate genera-
tion by other proteases (such as APN). In this context, different
tissues may present different metabolic signatures resulting
from DPP4 action, depending on the underlying pathophysio-
logical conditions.
Through its enzymatic activity, DPP4 can inactivate sev-
eral inflammatory mediators, such as Mig (CXCL9), IP-10
(CXCL10), and I-TAC (CXCL11), greatly reducing their che-
motactic activity, although without hindering antiangiogenic
activity.86 Conversely, cleavage of chemokine LD78β by CD26/
DPP4 significantly enhanced its lymphocyte and monocyte che-
motactic properties.87 In addition, DPP4-truncated products
show different receptor interaction22 and selectivity88 compared
with their noncleaved precursor peptide. Drugs acting on these
pathways can, therefore, have different net effects. Further re-
search is warranted to assess for significant differences between
truncated or nontruncated forms, with a comprehensive assess-
ment of their regulatory mechanisms and their relevance to the
inflammatory milieu.
In our systematic review, all studies showed at least a
moderate therapeutic benefit of DPP4i in animal models of co-
litis. On the one hand, these results reflect the inhibition of the
catalytic activity of DDP4i over bioactive substrates such as
GLP-2, GLP-1, and VIP, greatly extending their half-lives. This
indirectly inhibits costimulatory signals of T-cell activation and
the production of Th1-polarizing cytokines and chemokines
while promoting intestinal proliferation and tissue recovery
(Fig. 1). On the other hand, a more direct effect of DPP4i action
cannot be excluded becuase CD26−/− mice did not possess any
inherent resistance to colitis development, nor did they display
an enhanced rate of repair of the damaged mucosal tissue. The
protective effect of DPP4i was only observed in the presence of
DPP4/CD26, suggesting that DPP4i may have unknown mech-
anisms of action besides blocking catalytic activity.53, 72, 73
In line with these findings, all animal studies with GLP-2
and GLP-1 analogs showed a clear benefit (Supplementary
Table 1) regarding intestinal proliferation, preservation of
tissue architecture, and prevention of weight loss in the setting
of induced inflammatory lesions. This is supported by similarly
positive findings in reports using drugs that induce the release
of endogenous GLP-1 and GLP-2, such as GPR4058 and TGR5
agonists.64
The extrapolation of these data to humans is challenging.
One study74 enrolling patients with moderate to severe CD
treated with the GLP-2 analog teduglutide failed to achieve sig-
nificance from placebo, although a trend toward remission was
observed (Table 1). However, this report was limited because it
was based on a pilot study with a relatively small sample size.
Moreover, the study had a high dropout rate, especially due to
adverse effects (up to 31%) and uncomfortable posology (daily
subcutaneous injections).
Lower expression of GLP-2R was reported in IBD pa-
tients vs controls, further significant reduction was reported in
inflamed tissue vs healthy samples, ans a significant decrease
was reported in the expression of serum GLP-2.50, 67 One re-
port, however, found no significant differences between IBD
patients and controls in tissue content or plasma concentration
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Dipeptidyl Peptidase 4 as a Therapeutic Target and Serum Biomarker in IBD
Inflamm Bowel Dis • Volume 27, Number 7, July 2021
of GPL-2 or PYY after meal stimulation.78 Wheter this is a
cause or a consequence of the underlying pathological process
remains to be elucidated. Still, the use of GLP-2 analogs and
DPP4i in IBD is a double-edged sword. Despite their benefits,
these drugs promote GLP-2-dependent intestinal tumor cell
proliferation and migratory activity,89 which may be of concern
in IBD patients who are already at higher risk of developing co-
lorectal carcinoma.1, 2 Further research is needed to assess their
viability and safety as IBD drugs.
Despite their anti-inflammatory effects, DPP4i also
block DPP4-mediated degradation of pro-inflammatory
chemokines,86 possibly contributing to the perpetuation of in-
flammatory stimuli. As such, one could argue that DPP4 inhibi-
tion enhances certain pro-inflammatory pathways and leads to
either a new onset or a flare-up of the underlying IBD or other
inflammatory conditions. Nevertheless, a recent metanalysis
did not find an increased risk of IBD in patients under DPP4i
therapy.90 This same mechanism can also be beneficial in spe-
cific pathologies. A recent study by Barreira da Silva et al91
showed that DPP4 inhibition prevented CXCL10 truncation
(and inactivation) and enhanced CXCR3-mediated antitumor
immunity and trafficking of T cells into the tumor parenchyma.
Furthermore, DPP4 is cleaved by a not fully understood mech-
anism (eg, shedding), and its soluble form, which is excreted
to plasma, may have yet uncharacterized endocrinological
effects.10
Aminopeptidase N acts in synergy with DPP4 for the reg-
ulation of immune responses by cleaving peptides preprocessed
by DPP4 or by generating substrates susceptible to cleavage by
DPP4.92 Dual inhibition of APN/DPP4 had statistically signif-
icant beneficial effects in animal models of colitis and may be
of clinical significance as a new direct or adjuvant treatment
modality in many pathologies.43, 93
In recent studies, human Th17 cells were implicated in the
pathogenesis of many autoimmune diseases, including IBD94; this
represents a step forward from the previous dichotomous Th1/Th2
paradigm. Bengsch et al95 demonstrated that CD26++ (highly ex-
pressing) cells express typical markers of type 17 differentiation,
even before stimulation, suggesting that CD26++ T cells harbor the
Th17 lineage. Moreover, Th1 and Th2 cells were shown to be com-
patible with an intermediate CD26+ phenotype, whereas regulatory
CD25+CD127−FOXP3+ IL-10-producing T cells showed an even
lower expression. Patients with active IBD were found to have the
highest frequency of tissue-infiltrating Th17 cells. A strong increase
was observed in inflamed tissue lesions, where 25%–50% of CD26++
T cells produced IL-17 upon stimulation, in contrast to peripheral
blood, where only about 5% of CD26++ T cells produced IL-17.
These findings suggest an incomplete differentiation of Th17 cells
in peripheral blood due to the lack of sufficient stimulatory signals
found in the proinflammatory cytokine-rich environment of lesion
sites. Thus, a link has been established between CD26 and Th17,
corroborating the preponderant role of CD26 in autoimmunity.
In the dawning of the microbiome age, DPP4 gains even
more interest. A recent proof-of-concept study demonstrated a
DPP4-like activity of gut microbiota,96 extending toward un-
charted territories the importance of intestinal microbiome–
host interactions in pathological settings.59, 97
Dipeptidyl peptidase 4 is also a potential serum bio-
marker for many diseases, including cancer and IBD, which have
become an intense target of investigation in recent years.77, 98
As evidenced in recent studies, sDPP4 levels and activity are sig-
nificantly lower in IBD patients vs healthy controls, and sDPP4
correlated negatively with other disease activity markers such
as C-reactive protein, orosomucoid and fecal calprotectin, and
disease activity scores (Harvey-Bradshaw Index [HBI], partial
Mayo Score [pMS], Crohn’s Disease Activity Index [CDAI],
and Truelove and Witts index [TW]) and endoscopic activity
groups.75–77, 80, 82 As reported in our previous study,77 an impor-
tant benefit of the use of sDPP4 as a biomarker is the ability to
predict the need for treatment escalation from baseline sDPP4
levels at an early stage of the disease process. This enables the
identification of patients who would benefit a priori from a
more aggressive treatment strategy, avoiding exposure to po-
tentially ineffective drugs and the consequent risk of adverse ef-
fects. A biomarker that could direct clinicians to more effective
treatment options (skipping the necessary steps of treatment
escalation with safety) may, at the end of the road, prove to be
more efficient and resource-sparing, and enable a faster con-
trol of the underlying disease. This translates to obvious gains
for the patient in terms of time, expenses, and quality of life.
Higher-powered prospective studies with larger sample sizes are
needed to confirm these findings and prove their usefulness in a
clinical real-world setting.77
This review includes 45 studies and is, to the best of our
knowledge, the first attempt to systematize the role of DPP4,
APN, and related substrates in IBD. It also provides, for the
first time, an overview of the integration of the underlying
pathophysiological processes and potential applications in clin-
ical practice. We highlight our translational approach to this
subject (from preclinical animal models of disease to studies in
IBD patients), which allowed to emphasize the existing know-
ledge gaps within and between both settings.
Nevertheless, this systematic review is hindered by some
limitations. Stemming from the inherent limitations of the in-
cluded reports, the overall quality of preclinical experimental
studies was less than desirable. As illustrated in Supplementary
Table 2, protocol variations within the “same” model and
the considerable variability of animal strains and species
do not allow for a reliable comparison between experiments.
Underreporting of the protocol execution and the subjec-
tive nature of the quality assessment tools also limit the in-
ternal validity and the extrapolation of data from animal to
human subjects. Most reports with human populations suf-
fered for having a cross-sectional design (only one study was
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Inflamm Bowel Dis • Volume 27, Number 7, July 2021
a prospective cohort77) or low sample size (Table 1), and only
one74 had an interventional approach akin to animal studies.
CONCLUSION
Despite the ubiquitous position and wide spectrum of
interactions of these ectopeptidases intertwining with many
known—yet poorly understood—pathophysiological processes,
their diagnostic and therapeutic benefits may be soon applied
to the growing roster of clinical tools for the management of
IBD. Still, many concerns regarding their potential for stimu-
lating carcinogenesis and immune dysregulation and their via-
bility as biomarkers still need to be evaluated in depth. Further
research is required to achieve the necessary data robustness
to introduce these new applications into clinical practice with
confidence and safety.
SUPPLEMENTARY DATA
Supplementary data is available at Inflammatory Bowel Dis-
eases online.
ACKNOWLEDGEMENTS
The authors thank Paula Pinto, PharmD, PhD (PMA,
Pharmaceutical Medicine Academy) for providing medical
writing and editorial assistance.
REFERENCES
1. Torres J, Mehandru S, Colombel JF, et al. Crohn’s disease. Lancet.
2017;389:1741–1755.
2. Ordás I, Eckmann L, Talamini M, et al. Ulcerative colitis. Lancet.
2012;380:1606–1619.
3. Guindi M, Riddell RH. Indeterminate colitis. J Clin Pathol. 2004;57:1233–1244.
4. Greuter T, Vavricka SR. Extraintestinal manifestations in inflammatory bowel
disease - epidemiology, genetics, and pathogenesis. Expert Rev Gastroenterol
Hepatol. 2019;13:307–317.
5. Lambeir AM, Durinx C, Scharpé S, et al. Dipeptidyl-peptidase IV from bench to
bedside: an update on structural properties, functions, and clinical aspects of the
enzyme DPP IV. Crit Rev Clin Lab Sci. 2003;40:209–294.
6. Deacon CF, Holst JJ, Carr RD. Glucagon-like peptide-1: a basis for new ap-
proaches to the management of diabetes. Drugs Today (Barc). 1999;35:159–170.
7. Mest HJ, Mentlein R. Dipeptidyl peptidase inhibitors as new drugs for the treat-
ment of type 2 diabetes. Diabetologia. 2005;48:616–620.
8. Cuchacovich M, Gatica H, Pizzo SV, et al. Characterization of human serum
dipeptidyl peptidase IV (CD26) and analysis of its autoantibodies in patients
with rheumatoid arthritis and other autoimmune diseases. Clin Exp Rheumatol.
2001;19:673–680.
9. Klemann C, Wagner L, Stephan M, et al. Cut to the chase: a review of CD26/
dipeptidyl peptidase-4’s (DPP4) entanglement in the immune system. Clin Exp
Immunol. 2016;185:1–21.
10. Röhrborn D, Eckel J, Sell H. Shedding of dipeptidyl peptidase 4 is mediated by
metalloproteases and up-regulated by hypoxia in human adipocytes and smooth
muscle cells. FEBS Lett. 2014;588:3870–3877.
11. Ohnuma K, Yamochi T, Uchiyama M, et al. CD26 mediates dissociation of Tollip
and IRAK-1 from caveolin-1 and induces upregulation of CD86 on antigen-
presenting cells. Mol Cell Biol. 2005;25:7743–7757.
12. Torimoto Y, Dang NH, Vivier E, et al. Coassociation of CD26 (dipeptidyl
peptidase IV) with CD45 on the surface of human T lymphocytes. J Immunol.
1991;147:2514–2517.
13. Trowbridge IS, Thomas ML. CD45: an emerging role as a protein tyrosine phos-
phatase required for lymphocyte activation and development. Annu Rev Immunol.
1994;12:85–116.
14. Martín M, Huguet J, Centelles JJ, et al. Expression of ecto-adenosine deaminase
and CD26 in human T cells triggered by the TCR-CD3 complex. Possible role of
adenosine deaminase as costimulatory molecule. J Immunol. 1995;155:4630–4643.
15. Pacheco R, Martinez-Navio JM, Lejeune M, et al. CD26, adenosine deaminase,
and adenosine receptors mediate costimulatory signals in the immunological syn-
apse. Proc Natl Acad Sci U S A. 2005;102:9583–9588.
16. Zhu T, Wu XL, Zhang W, et al. Glucagon like Peptide-1 (GLP-1) modulates
OVA-induced airway inflammation and mucus secretion involving a protein ki-
nase A (PKA)-dependent nuclear factor-κB (NF-κB) signaling pathway in mice.
Int J Mol Sci. 2015;16:20195–20211.
17. Vahl TP, Paty BW, Fuller BD, et al. Effects of GLP-1-(7-36)NH2, GLP-1-(7-37),
and GLP-1- (9-36)NH2 on intravenous glucose tolerance and glucose-induced
insulin secretion in healthy humans. J Clin Endocrinol Metab. 2003;88:1772–1779.
18. Pedersen J, Pedersen NB, Brix SW, et al. The glucagon-like peptide 2 receptor is
expressed in enteric neurons and not in the epithelium of the intestine. Peptides.
2015;67:20–28.
19. Leen JL, Izzo A, Upadhyay C, et al. Mechanism of action of glucagon-like
peptide-2 to increase IGF-I mRNA in intestinal subepithelial fibroblasts.
Endocrinology. 2011;152:436–446.
20. Bjerknes M, Cheng H. Modulation of specific intestinal epithelial progenitors by
enteric neurons. Proc Natl Acad Sci U S A. 2001;98:12497–12502.
21. Fesler Z, Mitova E, Brubaker PL. GLP-2, EGF, and the intestinal epithe-
lial IGF-1 receptor interactions in the regulation of crypt cell proliferation.
Endocrinology. 2020;161. doi: 10.1210/endocr/bqaa040.
22. Thulesen J, Knudsen LB, Hartmann B, et al. The truncated metabolite GLP-2
(3-33) interacts with the GLP-2 receptor as a partial agonist. Regul Pept.
2002;103:9–15.
23. Kochar B, Long MD, Shelton E, et al. Safety and efficacy of teduglutide (Gattex)
in patients with Crohn’s disease and need for parenteral support due to short bowel
syndrome-associated intestinal failure. J Clin Gastroenterol. 2017;51:508–511.
24. de Heuvel E, Wallace L, Sharkey KA, Sigalet DL. Glucagon-like peptide 2
induces vasoactive intestinal polypeptide expression in enteric neurons via
phophatidylinositol 3-kinase-γ signaling. Am J Physiol Endocrinol Metab.
2012;303:E994–1005.
25. Domschke S, Domschke W, Bloom SR, et al. Vasoactive intestinal peptide in man:
pharmacokinetics, metabolic and circulatory effects. Gut. 1978;19:1049–1053.
26. Iwasaki M, Akiba Y, Kaunitz JD. Recent advances in vasoactive intestinal
peptide physiology and pathophysiology: focus on the gastrointestinal system.
F1000Research. 2019;8:1629.
27. Delgado M, Munoz-Elias EJ, Gomariz RP, et al. Vasoactive intestinal peptide
and pituitary adenylate cyclase-activating polypeptide prevent inducible nitric
oxide synthase transcription in macrophages by inhibiting NF-kappa B and IFN
regulatory factor 1 activation. J Immunol. 1999;162:4685–4696.
28. Delgado M, Gonzalez-Rey E, Ganea D. VIP/PACAP preferentially attract Th2
effectors through differential regulation of chemokine production by dendritic
cells. Faseb J. 2004;18:1453–1455.
29. McClellan JB Jr, Garner CW. Purification and properties of human intestine ala-
nine aminopeptidase. Biochim Biophys Acta. 1980;613:160–167.
30. Ansorge S, Bank U, Heimburg A, et al. Recent insights into the role of dipeptidyl
aminopeptidase IV (DPIV) and aminopeptidase N (APN) families in immune
functions. Clin Chem Lab Med. 2009;47:253–261.
31. Hoffmann T, Faust J, Neubert K, et al. Dipeptidyl peptidase IV (CD 26) and
aminopeptidase N (CD 13) catalyzed hydrolysis of cytokines and peptides with
N-terminal cytokine sequences. FEBS Lett. 1993;336:61–64.
32. Biton A, Bank U, Täger M, et al. Dipeptidyl peptidase IV (DP IV, CD26) and
aminopeptidase N (APN, CD13) as regulators of T cell function and targets
of immunotherapy in CNS inflammation. In: Lendeckel U, Reinhold D, Bank
U, (eds). Dipeptidyl Aminopeptidases. Boston, MA: Springer US; 177–186. doi:
10.1007/0-387-32824-6_19.
33. Jurjus AR, Khoury NN, Reimund JM. Animal models of inflammatory bowel
disease. J Pharmacol Toxicol Methods. 2004;50:81–92.
34. Moher D, Liberati A, Tetzlaff J, et al.; PRISMA Group. Preferred reporting items
for systematic reviews and meta-analyses: the PRISMA statement. Plos Med.
2009;6:e1000097.
35. Hooijmans CR, Rovers MM, de Vries RB, et al. SYRCLE’s risk of bias tool for
animal studies. BMC Med Res Methodol. 2014;14:43.
36. Critical Appraisal Skills Programme (2019). CASP Qualitative Checklist. https://
casp-uk.net/wp-content/uploads/2018/01/CASP-Qualitative-Checklist-2018.pdf.
Accessed June 24, 2020.
37. Critical Appraisal Skills Programme (2019). CASP Cohort Checklist. https://
casp-uk.net/wp-content/uploads/2018/01/CASP-Cohort-Study-Checklist_2018.
pdf. Accessed June 24, 2020.
38. Alavi K, Schwartz MZ, Palazzo JP, et al. Treatment of inflammatory bowel di-
sease in a rodent model with the intestinal growth factor glucagon-like peptide-2.
J Pediatr Surg. 2000;35:847–851.
39. Alters SE, McLaughlin B, Spink B, et al. GLP2-2G-XTEN: a pharmaceutical
protein with improved serum half-life and efficacy in a rat Crohn’s disease model.
Plos One. 2012;7:e50630.
40. Anbazhagan AN, Thaqi M, Priyamvada S, et al. GLP-1 nanomedicine alleviates
gut inflammation. Nanomedicine. 2017;13:659–665.
41. Arthur GL, Schwartz MZ, Kuenzler KA, et al. Glucagonlike peptide-2 analogue:
a possible new approach in the management of inflammatory bowel disease. J
Pediatr Surg. 2004;39:448–452; discussion 448.
42. Ban H, Bamba S, Imaeda H, et al. The DPP-IV inhibitor ER-319711 has a pro-
liferative effect on the colonic epithelium and a minimal effect in the amelioration
of colitis. Oncol Rep. 2011;25:1699–1703.
Downloaded from https://academic.oup.com/ibdjournal/article/27/7/1153/6028655 by University Library Zurich / Zentralbibliothek Zurich user on 31 December 2022
1165
Dipeptidyl Peptidase 4 as a Therapeutic Target and Serum Biomarker in IBD
Inflamm Bowel Dis • Volume 27, Number 7, July 2021
43. Bank U, Heimburg A, Helmuth M, et al. Triggering endogenous immunosup-
pressive mechanisms by combined targeting of Dipeptidyl peptidase IV (DPIV/
CD26) and Aminopeptidase N (APN/ CD13)–a novel approach for the treatment
of inflammatory bowel disease. Int Immunopharmacol. 2006;6:1925–1934.
44. Baticic L, Detel D, Kucic N, et al. Neuroimmunomodulative properties of
dipeptidyl peptidase IV/CD26 in a TNBS-induced model of colitis in mice. J Cell
Biochem. 2011;112:3322–3333.
45. Boushey RP, Yusta B, Drucker DJ. Glucagon-like peptide 2 decreases mortality
and reduces the severity of indomethacin-induced murine enteritis. Am J Physiol.
1999;277:E937–E947.
46. Buljevic S, Detel D, Pugel EP, et al. The effect of CD26-deficiency on dipeptidyl
peptidase 8 and 9 expression profiles in a mouse model of Crohn’s disease. J Cell
Biochem. 2018;119:6743–6755.
47. Detel D, Buljevic S, Pucar LB, et al. Influence of CD26/dipeptidyl peptidase IV
deficiency on immunophenotypic changes during colitis development and resolu-
tion. J Physiol Biochem. 2016;72:405–419.
48. Detel D, Pugel EP, Pucar LB, et al. Development and resolution of colitis in mice
with target deletion of dipeptidyl peptidase IV. Exp Physiol. 2012;97:486–496.
49. Drucker DJ, Yusta B, Boushey RP, et al. Human [Gly2]GLP-2 reduces the severity of co-
lonic injury in a murine model of experimental colitis. Am J Physiol. 1999;276:G79–G91.
50. El-Jamal N, Erdual E, Neunlist M, et al. Glugacon-like peptide-2: broad receptor
expression, limited therapeutic effect on intestinal inflammation and novel role in
liver regeneration. Am J Physiol Gastrointest Liver Physiol. 2014;307:G274–G285.
51. Elkatary R, Abdelrahman K, Hassanin A, et al. Effect of different doses of
sitagliptin in treatment of experimentally induced colitis in mice. Br J Pharm Res.
2015;7:140–151.
52. Fujiwara K, Inoue T, Yorifuji N, et al. Combined treatment with dipeptidyl pep-
tidase 4 (DPP4) inhibitor sitagliptin and elemental diets reduced indomethacin-
induced intestinal injury in rats via the increase of mucosal glucagon-like
peptide-2 concentration. J Clin Biochem Nutr. 2015;56:155–162.
53. Geier MS, Tenikoff D, Yazbeck R, et al. Development and resolution of exper-
imental colitis in mice with targeted deletion of dipeptidyl peptidase IV. J Cell
Physiol. 2005;204:687–692.
54. Gu J, Liu J, Huang T, et al. The protective and anti-inflammatory effects of a
modified glucagon-like peptide-2 dimer in inflammatory bowel disease. Biochem
Pharmacol. 2018;155:425–433.
55. Inoue T, Higashiyama M, Kaji I, et al. Dipeptidyl peptidase IV inhibition pre-
vents the formation and promotes the healing of indomethacin-induced intestinal
ulcers in rats. Dig Dis Sci. 2014;59:1286–1295.
56. Iwaya H, Fujii N, Hagio M, et al. Contribution of dipeptidyl peptidase IV to
the severity of dextran sulfate sodium-induced colitis in the early phase. Biosci
Biotechnol Biochem. 2013;77:1461–1466.
57. Kamysz E, Sałaga M, Sobocińska M, et al. Anti-inflammatory effect of novel
analogs of natural enkephalinase inhibitors in a mouse model of experimental
colitis. Future Med Chem. 2016;8:2231–2243.
58. Kato S, Utsumi D, Matsumoto K. G protein-coupled receptor 40 activation
ameliorates dextran sulfate sodium-induced colitis in mice via the upregulation
of glucagon-likepeptide-2. J Pharmacol Sci. 2019;140:144–152.
59. Lee SJ, Lee J, Li KK, et al. Disruption of the murine Glp2r impairs Paneth cell
function and increases susceptibility to small bowel enteritis. Endocrinology.
2012;153:1141–1151.
60. L’Heureux MC, Brubaker PL. Glucagon-like peptide-2 and common therapeutics
in a murine model of ulcerative colitis. J Pharmacol Exp Ther. 2003;306:347–354.
61. Mimura S, Ando T, Ishiguro K, et al. Dipeptidyl peptidase-4 inhibitor anagliptin
facilitates restoration of dextran sulfate sodium-induced colitis. Scand J
Gastroenterol. 2013;48:1152–1159.
62. Qi KK, Lv JJ, Wu J, Xu ZW. Therapeutic effects of different doses of polyeth-
ylene glycosylated porcine glucagon-like peptide-2 on ulcerative colitis in male
rats. BMC Gastroenterol. 2017;17:34.
63. Qi KK, Wu J, Wan J, et al. Purified PEGylated porcine glucagon-like peptide-2
reduces the severity of colonic injury in a murine model of experimental colitis.
Peptides. 2014;52:11–18.
64. Sakanaka T, Inoue T, Yorifuji N, et al. The effects of a TGR5 agonist and a
dipeptidyl peptidase IV inhibitor on dextran sulfate sodium-induced colitis in
mice. J Gastroenterol Hepatol. 2015;30(Suppl 1):60–65.
65. Salaga M, Binienda A, Draczkowski P, et al. Novel peptide inhibitor of dipeptidyl
peptidase IV (Tyr-Pro-D-Ala-NH2) with anti-inflammatory activity in the mouse
models of colitis. Peptides. 2018;108:34–45.
66. Salaga M, Mokrowiecka A, Jacenik D, et al. Systemic administration of
sialorphin attenuates experimental colitis in mice via interaction with mu and
kappa opioid receptors. J Crohns Colitis. 2017;11:988–998.
67. Salaga M, Mokrowiecka A, Zielinska M, et al. New peptide inhibitor of
dipeptidyl Peptidase IV, EMDB-1 extends the half-life of GLP-2 and at-
tenuates colitis in mice after topical administration. J Pharmacol Exp Ther.
2017;363:92–103.
68. Schmidt PT, Hartmann B, Bregenholt S, et al. Deficiency of the intestinal growth
factor, glucagon-like peptide 2, in the colon of SCID mice with inflammatory
bowel disease induced by transplantation of CD4+ T cells. Scand J Gastroenterol.
2000;35:522–527.
69. Wu J, Qi K, Xu Z, Wan J. Glucagon-like peptide-2-loaded microspheres as treat-
ment for ulcerative colitis in the murine model. J Microencapsul. 2015;32:598–607.
70. Yang PY, Zou H, Lee C, et al. Stapled, long-acting glucagon-like peptide 2 an-
alog with efficacy in dextran sodium sulfate induced mouse colitis models. J Med
Chem. 2018;61:3218–3223.
71. Yazbeck R. Inhibiting dipeptidyl peptidase activity partially ameliorates colitis in
mice. Front Biosci. 2008;13:6850.
72. Yazbeck R, Howarth GS, Butler RN, et al. Biochemical and histological changes
in the small intestine of mice with dextran sulfate sodium colitis. J Cell Physiol.
2011;226:3219–3224.
73. Yazbeck R, Sulda ML, Howarth GS, et al. Dipeptidyl peptidase expression
during experimental colitis in mice. Inflamm Bowel Dis. 2010;16:1340–1351.
74. Buchman AL, Katz S, Fang JC, et al.; Teduglutide Study Group. Teduglutide, a
novel mucosally active analog of glucagon-like peptide-2 (GLP-2) for the treat-
ment of moderate to severe Crohn’s disease. Inflamm Bowel Dis. 2010;16:962–973.
75. Magro DO, Kotze PG, Martinez CAR, et al. Changes in serum levels of lipopoly-
saccharides and CD26 in patients with Crohn’s disease. Intest Res. 2017;15:352–357.
76. Moran GW, O’Neill C, Padfield P, et al. Dipeptidyl peptidase-4 expression is re-
duced in Crohn’s disease. Regul Pept. 2012;177:40–45.
77. Pinto-Lopes P, Afonso J, Pinto-Lopes R, et al. Serum dipeptidyl peptidase 4:
a predictor of disease activity and prognosis in inflammatory bowel disease.
Inflamm Bowel Dis. 2020;XX:1–13.
78. Schmidt PT, Ljung T, Hartmann B, et al. Tissue levels and post-prandial secretion
of the intestinal growth factor, glucagon-like peptide-2, in controls and inflam-
matory bowel disease: comparison with peptide YY. Eur J Gastroenterol Hepatol.
2005;17:207–212.
79. Tsukahara T, Watanabe K, Watanabe T, et al. Tumor necrosis factor α decreases
glucagon-like peptide-2 expression by up-regulating G-protein-coupled receptor
120 in Crohn disease. Am J Pathol. 2015;185:185–196.
80. Varljen J, Sinčić BM, Batičić L, et al. Clinical relevance of the serum dipeptidyl
peptidase IV (DPP IV/CD26) activity in adult patients with Crohn’s disease and
Ulcerative colitis. Croat Chem Acta. 2005;78:427–432.
81. Xiao Q, Boushey RP, Cino M, et al. Circulating levels of glucagon-like peptide-2
in human subjects with inflammatory bowel disease. Am J Physiol Regul Integr
Comp Physiol. 2000;278:R1057–R1063.
82. Hildebrandt M, Rose M, Rüter J, et al. Dipeptidyl peptidase IV (DP IV,
CD26) in patients with inflammatory bowel disease. Scand J Gastroenterol.
2001;36:1067–1072.
83. Kimura I, Ichimura A, Ohue-Kitano R, et al. Free fatty acid receptors in health
and disease. Physiol Rev. 2020;100:171–210.
84. Guo C, Chen WD, Wang YD. TGR5, not only a metabolic regulator. Front
Physiol. 2016;7:646.
85. Milligan G, Alvarez-Curto E, Hudson BD, et al. FFA4/GPR120: pharmacology
and therapeutic opportunities. Trends Pharmacol Sci. 2017;38:809–821.
86. Proost P, Schutyser E, Menten P, et al. Amino-terminal truncation of CXCR3
agonists impairs receptor signaling and lymphocyte chemotaxis, while preserving
antiangiogenic properties. Blood. 2001;98:3554–3561.
87. Proost P, Menten P, Struyf S, et al. Cleavage by CD26/dipeptidyl peptidase IV
converts the chemokine LD78beta into a most efficient monocyte attractant and
CCR1 agonist. Blood. 2000;96:1674–1680.
88. Grandt D, Schimiczek M, Rascher W, et al. Neuropeptide Y 3-36 is an endoge-
nous ligand selective for Y2 receptors. Regul Pept. 1996;67:33–37.
89. Masur K, Schwartz F, Entschladen F, et al. DPPIV inhibitors extend GLP-2
mediated tumour promoting effects on intestinal cancer cells. Regul Pept.
2006;137:147–155.
90. Radel JA, Pender DN, Shah SA. Dipeptidyl peptidase-4 inhibitors and inflamma-
tory bowel disease risk: a meta-analysis. Ann Pharmacother. 2019;53:697–704.
91. Barreira da Silva R, Laird ME, Yatim N, et al. Dipeptidylpeptidase 4 inhibition
enhances lymphocyte trafficking, improving both naturally occurring tumor im-
munity and immunotherapy. Nat Immunol. 2015;16:850–858.
92. Lendeckel U, Arndt M, Bukowska A, et al. Synergistic action of DPIV and APN
in the regulation of T cell function. In: Hildebrandt M, Klapp BF, Hoffman T,
Demuth H-U, (eds). Dipeptidyl Aminopeptidases in Health and Disease. Boston,
MA: Springer; 123–131. doi: 10.1007/0-306-47920-6_16.
93. Bank U, Tadje J, Helmuth M, et al. Dipeptidylpeptidase IV (DPIV) and alanyl-
aminopeptidases (AAPs) as a new target complex for treatment of autoimmune
and inflammatory diseases-proof of concept in a mouse model of colitis. Adv Exp
Med Biol. 2006;575:143–153.
94. Miossec P, Korn T, Kuchroo VK. Interleukin-17 and type 17 helper T cells. N
Engl J Med. 2009;361:888–898.
95. Bengsch B, Seigel B, Flecken T, et al. Human Th17 cells express high levels of enzy-
matically active dipeptidylpeptidase IV (CD26). J Immunol. 2012;188:5438–5447.
96. Olivares M, Schüppel V, Hassan AM, et al. The potential role of the dipeptidyl
peptidase-4-like activity from the gut microbiota on the host health. Front
Microbiol. 2018;9:1900.
97. Ryan PM, Patterson E, Carafa I, et al. Metformin and dipeptidyl peptidase-4 in-
hibitor differentially modulate the intestinal microbiota and plasma metabolome
of metabolically dysfunctional mice. Can J Diabetes. 2020;44:146–155.e2.
98. Enz N, Vliegen G, De Meester I, et al. CD26/DPP4 - a potential biomarker and
target for cancer therapy. Pharmacol Ther. 2019;198:135–159.
Downloaded from https://academic.oup.com/ibdjournal/article/27/7/1153/6028655 by University Library Zurich / Zentralbibliothek Zurich user on 31 December 2022